Blade lock



Jan. 3, 1967 H. NICKLES 3,295,826

BLADE LOCK Filed April 8, 1966 INVENTOR [Em/fence /z fife/Wes ATTORNEY United States Patent Ofiice 3,295,826 Patented Jam 3, 1957 3,295,826 BLADE LOCK 7 Lawrence H. Nickles, Indianapolis, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Apr. 8, 1966, Ser. No. 541,178 Claims. (Cl. 253-77) My invention relates to turbomachines and, more par ticularly, to a means for securing blades or the like to a rotor.

The invention is especially applicable to axial flow elastic fluid turbine and compressor rotors having blades removably dovetailed thereto. The blades of such machines are usually secured to the rotor by inserting the roots of the blades in grooves in the rim of the rotor, and by doweling the roots to the rim to restrain them from axial movement within the grooves. The doweling is accomplished by providing communicating passages in the blade roots and the rotor rim and by inserting dowels in the passages. My invention is directed toward providing a simplified arrangement for retaining the dowels in the passages without deforming the rotor rim.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the present invention is clearly shown.

In the drawings:

FIGURE 1 is an axial section of the rim portion of a turbine rotor and a turbine blade having its root portion secured thereto by doweling according to my invention.

FIGURE 2 is a perspective view of the turbine blade shown in FIGURE 1.

FIGURE 3 is an enlargement of a portion of FIGURE 1 illustrating the dowel partially inserted in the rotor rim passage prior to its insertion in the turbine blade root passage, and

FIGURE 4 is a section taken substantially along line 44 of FIGURE 1 and looking in the direction of the arrows.

Referring now to the drawings, a circumferential row of radially projecting blades are secured to the rim portion of a turbomachine rotor 12, which may take the form of a single gas turbine wheel or disk as illustrated. The blades 10 include a ca-mbered blade portion 14 and a root portion 16 which may be grooved to the conventional fir tree configuration illustrated. The rim 17 of the turbine disk 12 is provided with a circumferential row of complemental slots or grooves 18 to receive the blade roots 16. The grooves 18 extend between the side faces 20 and 22 of the turbine disk so that the blade roots 16 may be inserted axially into the grooves 18. The fir tree dovetail comprises the usual interengaging dovetail parts on the root and the rotor extending transversely of the rim to secure the blades to the rotor radially and tangentially. Each blade root 16 is provided with a slot 24 which is located for communication with a generally radial bore or passage 26 in the rotor rim. The slot 24 has a dome-shaped roof and extends the entire width of the root 16. The bores 26 extend between the bottoms of the rotor grooves 18 and an inner circumferential face 23 of the rim. Each blade root is secured in its rotor groove by a dowel pin 28 which is inserted in the rim passage and driven upwardly into the blade slot. The dowels 28 are hollow and thus easily deformed.

As the dowel 28 is driven upwardly into the blade slot 24 from the position shown in FIGURE 3 to that shown in FIGURE 1, its upper edge engages rounded cam surfaces formed by the dome-shaped top of the blade slot 24. Since the circumferential width of the blade loading slot 18 in the area of the blade slot 24 and the corresponding part of the blade groove 18 is larger than the diameter of thebore 26, the head of the hollow dowel 28 deforms narrowing inwardly toward an axial plane pass: ing through the center of the dowel and spreading outwardly along the circumferential plane perpendicular to it. This is best understood in reference to FIGURES 1 and 4; FIGURE 1 showing the axial plane 'while FIG- URE 4 illustrates the perpendicular circumferential plane. While I have illustrated a constant width groove 18 with a domed roof to provide cam surfaces, other configurations are possible. The important feature is that the groove converge in one direction and be wider than the hole 26 in the other direction. This could be accomplished, for example, by a V-shaped or trapezoidal groove in the blade root. After deformation, the head 30 is elliptical as opposed to the circular cross section of the remainder of dowel 28. The major diameter of the elliptical head is greater than diameter of bore 26 and thus the dowel 28 is automatically retained against removal. The dowels 28 are preferably shearable so that the removal of a blade from the rotor may be readily accomplished by driving the blade root axially out of the rotor groove 18. With the blade removed, the stub of the dowel can easily be driven out of the hole 26 and the head 30 can easily be driven axially out of the blade mounting slot 18.

While the preferred embodiment of the invention has been described fully in order to explain the principles of the invention, it is to be understood that modifications in structure may be made by the exercise of skill in the art within the scope of the invention, which is not to be regarded as limited by the detailed description of the preferred embodiment.

I claim:

1. A bladed rotor comprising: a rotor having a widened rim with a plurality of circumferentially spaced generally axial fir tree mounting grooves and a plurality of bores extending generally radially across said rim and in radial alignment with said mounting grooves, a plurality of blades having mating fir tree roots mounted in said grooves, each of said blade roots having a generally transverse slot bounded by a surface having a cam portion, said slots being in communication with said bores and having a width coextensive with said bore in a first plane, and a width greater than said bore in a second plane transverse to said first plane,

a dowel disposed in said bore and having a head deformable by said cam portion to a width greater than the width of said bore disposed in said slot whereby said dowel is retained in said bore and slot upon deformation of said head, said dowel fixing said blade axially with respect to said rotor.

2. The bladed rotor as defined in claim 1 wherein said slots have a width coextensive with said bores in the axial planes of the rotor and wherein said slots have a width greater than the width of said bores in a radial plane of said rotor.

3. The bladed rotor as defined in claim 1 wherein said slot is bounded by a continuous surface comprising generally fiat side walls parallelly spaced coextensively with said bore, and joined by a domed wall, said domed wall providing cam portions.

4. The bladed rotor as defined in claim 2 wherein said slot is bounded by a continuous surface comprising generally flat side walls parallelly spaced coextensively with said bore, and joined by a domed wall, said domed Wall providing cam portions.

. 5. The bladed rotor as defined in claim 4 wherein said 10 dowel is a hollow tube.

References Cited by the Examiner UNITED STATES PATENTS MARTIN -P. SCHWADRON, Primary Examiner.

E. A. POWELL, JR., Assistant Examiner. 

1. A BLADED ROTOR COMPRISING: A ROTOR HAVING A WIDENED RIM WITH A PLURALITY OF CIRCUMFERENTIALLY SPACED GENERALLY AXIAL FIR TREE MOUNTING GROOVES AND A PLURALITY OF BORES EXTENDING GENERALLY RADIALLY ACROSS SAID RIM AND IN RADIAL ALIGNMENT WITH SAID MOUNTING GROOVES, A PLURALITY OF BLADES HAVING MATING FIR TREE ROOTS MOUNTED IN SAID GROOVES, EACH OF SAID BLADE ROOTS HAVING A GENERALLY TRANSVERSE SLOT BOUNDED BY A SURFACE HAVING A CAM PORTION, SAID SLOTS BEING IN COMMUNICATION WITH SAID BORES AND HAVING A WIDTH COEXTENSIVE WITH SAID BORE IN A FIRST PLANE, AND A WIDTH GREATER THAN SAID BORE IN A SECOND PLANE TRANSVERSE TO SAID FIRST PLANE, A DOWEL DISPOSED IN SAID BORE AND HAVING A HEAD DEFORMABLE BY SAID CAM PORTION TO A WIDTH GREATER THAN THE WIDTH OF SAID BORE DISPOSED IN SAID SLOT WHEREBY SAID DOWEL IS RETAINED IN SAID BORE AND SLOT UPON DEFORMATION OF SAID HEAD, SAID DOWEL FIXING SAID BLADE AXIALLY WITH RESPECT TO SAID ROTOR. 